4th Grade - Prime Numbers

 
     
 
     
 
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4th
Numbers - large, small, prime and negative
Prime Numbers
Know that numbers such as 2, 3, 5, 7, and 11 do not have any factors except 1 and themselves and that such numbers are called prime numbers.
Identify numbers that can only be divided by one and themselves (i.e. 2, 3, 5, 7, 11, 13…)
 

Sample Problems

(1)

Write the factors for the number below. Is it prime or composite?

27: __________ _____________


(1, 3, 9, 27; composite)

(2)

Which number is not prime:

2, 3, 7, 13, 19, 21, 23


List the factors for the composite number: _______________________

(21; Factors: 1,3,7,21)

(3)

Which array does not relate to the product 16:

(a)

 

 

4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

 

 

 

 

 

 

 

 

 

 

 

 


(b)

 

 

 

 

 

8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2

 

 

 

 

 

 

 

 

 

 


(c)

 

 

 

 

 

 

 

1

6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


(d)

 

 

 

6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3

 

 

 

 

 

 

 

 


(d)

(4)

Complete the factor tree:

81

/ \

__ x __

/ \ / \

__ x __ __ x __


Write the prime numbers ___________________

(3 x 3 x 3 x3 =81)

(5)

Complete the factor tree:

56

/ \

__ x __

/ \ / \

__ x __ __ x __


Write the prime numbers _____________

(2 x 2 x 2 x 7= 56)

Learning Tips

(1)

Multiplication table:

Teach child to use the multiplication table to help find multiples and factors.

 

0

1

2

3

4

5

6

7

8

9

0

0

0

0

0

0

0

0

0

0

0

1

0

1

2

3

4

5

6

7

8

9

2

0

2

4

6

8

10

12

14

16

18

3

0

3

6

9

12

15

18

21

24

27

4

0

4

8

12

16

20

24

28

32

36

5

0

5

10

15

20

25

30

35

40

45

6

0

6

12

18

24

30

36

42

48

54

7

0

7

14

21

28

35

42

49

56

63

8

0

8

16

24

32

40

48

56

64

72

9

0

9

18

27

36

45

54

63

72

81



(2)



Arrays:

Review how to use arrays- the number of boxes shaded across (10) is one factor and the number of boxes shaded going down is another factor (4). There are 40 boxes completely shaded (4 x 10 = 40).

 

 

 

 

 

10

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


How to make arrays on the graph paper template:

  • Highlight the boxes desired

  • Click on format

  • Click on borders and shading

  • Click on shading

  • Fill with color preference

(3)

Math vocabulary:


Prime number- a number that only has two factors (1 and itself; For example, 3 only has two factors 1 x 3. Therefore, 3 is a prime number).

Composite number- a number that has more than two factors.


Factor Tree- A diagram that helps find prime factors of a product.

Product

/ \

factor x factor

/ \

__x __


12

/ \

6 x 2

/ \

2 x 3


1” is neither prime nor composite


(4)

Explain how to use factor trees:

Reminder: There can be various ways to begin the factor tree, as long as children get the same result of prime numbers at the end of the tree (highlighted numbers).


12

/ \

6 x 2

/ \

2 x 3


Write the product of prime numbers as: 2 x 2 x 3 = 12


OR



12

/ \

4 x 3

/ \

2 x 2


Write the product of prime numbers as: 2 x 2 x 3 =12


(5)

Practice basic multiplication and division facts:

Child will be more accurate and quick in determining factors for products.

Extra Help Problems

(1)

List the factors for the number below. Label prime or composite.


20: ________________ _____________


(1,2,4,5,10,20; composite)

(2)


List the factors for the number below. Label prime or composite


25: ________________ _____________


(1,5,25; composite)

(3)

List the factors for the number below. Label prime or composite


31: ________________ _____________


(1,31; prime)

(4)

List the factors for the number below. Label prime or composite


9: ________________ _____________


(1,3,9; composite)

(5)

List the factors for the number below. Label prime or composite

58: ________________ _____________


(1,2,29,58; composite)

(6)

Make an array for: 27


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Label prime or composite: ________________


(Arrays can be 1x27 or 3x9; composite)

(7)

Make an array for: 35


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Label prime or composite: ___________________


(Array can be1x35 or 5x7; composite)

(8)


Make an array for: 19


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Label prime or composite: _________________________

(Array 1x19; prime)

(9)

Make an array for : 121


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Label prime or composite ___________________


(Array can be 1x121 or 11x 11)

(10)

Make an array for : 8


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Label prime or composite _______________________


(Arrays can be 1 x 8 or 2 x 4; composite)

(11)

Use a factor tree to find the prime factors for the product:


75

/ \

__ x __

/ \ / \

__ x __ __ x __


Write the prime factors as a product ___________________



(3 x 5 x 5 = 75)

(12)

Use a factor tree to find the prime factors for the product:


57

/ \

__ x __

/ \ / \

__ x __ __ x __


Write the prime factors as a product ___________________


(3 x 19 =57)

(13)

Use a factor tree to find the prime factors for the product:


98

/ \

__ x __

/ \ / \

__ x __ __ x __


Write the prime factors as a product ___________________

(2 x 7 x 7 =98)

(14)

Use a factor tree to find the prime factors for the product:




60

/ \

__ x __

/ \ / \

__ x __ __ x __


Write the prime factors as a product ___________________


(2 x 2 x 3 x 5= 60)

(15)


Use a factor tree to find the prime factors for the product:


22

/ \

__ x __

/ \ / \

__ x __ __ x __


Write the prime factors as a product ___________________

(2 x 11 =22)

(16)

Use a factor tree to find the prime factors for the product:


56

/ \

__ x __

/ \ / \

__ x __ __ x __


Write the prime factors as a product ___________________


(2 x 2 x 2 x 7=56)

(17)

Use a factor tree to find the prime factors for the product:


113

/ \

__ x __

/ \ / \

__ x __ __ x __


Write the prime factors as a product ___________________


(1 x 113)

(18)

Write the missing prime factor:

11 x 2 x ___ = 66


(3)

(19)

Write the missing prime factor:

2 x 2 x 2 x ___ x 5 = 120


(3)

(20)

Write the missing prime factor:

5 x ___ = 155


(31)

(21)

Which is a prime number:


  1. 4

  2. 52

  3. 39

  4. 37


(37)

(22)


Which number is not a factor of 12:

  1. 3

  2. 6

  3. 8


(8)

(23)

Which equations shows prime factors of 32:

  1. 8 x 2 x 2

  2. 2 x 2 x 2 x 3

  3. 2 x 2 x 2 x 2 x 2 x 2


(c)

(24)

What type of number is 1:

  1. prime

  2. composite

  3. both

  4. neither


(d)

(25)

What is the product for:

2 x 2 x 3 x 11 = ______


(132)

 

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